Ultrastructural characterization of oligodendroglial-like cells in central nervous system tumors

Prognostic Implications of Histological Clear Cells in High-Grade Intracranial Ependymal Tumors: A Retrospective Analysis from a Tertiary Care Hospital in Pakistan

Background:

Clear cell variant in ependymal tumors is rare. We aimed to compare the features and outcome of the World Health Organization (WHO) Grade 3 ependymal tumors with clear cells to the WHO Grade 3 classic anaplastic ependymoma (AE).

Materials and Methods:

A retrospective cohort study conducted at the Department of Neurosurgery, Aga Khan University, Pakistan, from 2003 to 2013. The medical records and radiology of patients with proven histopathology were reviewed. The analysis was done on SPSS 20.

Results:

Nine cases of clear cell variant and 23 cases of classic AE were found, both of which combined equated to 4% of the total tumor burden in 11 years. The median age of clear cell ependymoma (CCE) and AE were 49 and 37 years, respectively. Presenting symptoms included headache in 66% of CCE and 63% in AE, raised intracranial pressure accounting for 33% of CCE and 54% of AE, dizziness in 22% CCE and 39% AE, while seizures presented equally in both. Supratentorial location was observed in 77% CCE and 48% AE. Both showed hypointense signals on T1-weighted images of magnetic resonance imaging (MRI) while T2-weighted images showed hyperintensity in all cases of CCE but only 80% of AE. MRI characteristics such as the presence of cystic component were found in 89% of CCE and 68% of AE, necrosis in 33% CCE, and 22% AE, hemorrhagic in 22% CCE and 9% AE, and equivalent contrast enhancement. Gross total resection was achieved in 5 (55%) patients of CCE, compared to 6 (26%) patients in AE. Subtotal resection was done in 4 (44%) patients of CCE and 15 (65%) patients of AE. Radiotherapy was given to 5 (55%) patients of CCE and 12 (52%) patients of AE. Recurrence was observed in 77% cases of CCE and 70% of AE, with metastasis in 29% of AE and in only one patient of CCE. Repeat surgery was done in 3 (33%) cases of CCE and 8 (35%) cases of AE. Median progression-free survival and overall survival were 9 and 13 months, respectively, in CCE while 14 and 18 months, respectively, for AE.

Conclusion:

Clear cells in the WHO Grade 3 ependymal tumors are found mainly in a comparatively older adult population with a predilection for supratentorial location and are more aggressive in behavior with poorer outcome than AE.

Ependymal tumors with oligodendroglioma like clear cells: Experience from a tertiary care hospital in Pakistan

Background:

Ependymal tumors with oligodendroglioma like clear cells have never been reported from Pakistan. We aimed to see the features and outcomes of this rare entity.

Methods:

It was retrospective cohort conducted at the Department of Neurosurgery, Aga Khan University from 2003 to 2013. The medical records and radiology of patients with proven histopathology were reviewed. Analysis was done on SPSS 20.

Results:

Eleven cases of ependymal tumors with clear cells were found, which equated to 1.5% of the total tumor burden in 11 years. The median age was 49 years. Most common presenting symptom was headache 54.5%. Out of 11 patients, 9 patients had a supratentorial tumor. Magnetic resonance imaging showed hypointense signals on T1 and hyperintense signals on T2-weighted images in all cases. Contrast enhancement was found in 9 patients (77.8%), necrosis and hemorrhage was found in 4 (36%) and 3 (27%) patients, respectively. Immunohistochemistry showed glial fibrillary acidic protein and epithelial membrane antigen positivity in all cases. Ki-67 showed high proliferative index in 6 patients. According to the World Health Organization grading of ependymal tumors, 2 patients had Grade II tumors, and 9 patients had Grade III tumors with clear cells. Gross total resection was achieved in 6 (54.5%) and subtotal resection in 5 patients (45.4%). Recurrence was observed in 9 patients. Six patients died of the disease. Median progression-free survival and overall survival was 8 months and 10 months, respectively.

Conclusion:

Ependymal tumors with clear cells presented more commonly in Grade III lesions and were more aggressive in behavior with poorer outcome compared to similar studies.

Shh Signaling through the Primary Cilium Modulates Rat Oligodendrocyte Differentiation

Primary Cilia (PC) are a very likely place for signal integration where multiple signaling pathways converge. Two major signaling pathways clearly shown to signal through the PC, Sonic Hedgehog (Shh) and PDGF-Rα, are particularly important for the proliferation and differentiation of oligodendrocytes, suggesting that their interaction occurs in or around this organelle. We identified PC in rat oligodendrocyte precursor cells (OPCs) and found that, while easily detectable in early OPCs, PC are lost as these cells progress to terminal differentiation. We confirmed the interaction between these pathways, as cyclopamine inhibition of Hedgehog function impairs both PDGF-mediated OPC proliferation and Shh-dependent cell branching. However, we failed to detect PDGF-Rα localization into the PC. Remarkably, ciliobrevin-mediated disruption of PC and reduction of OPC process extension was counteracted by recombinant Shh treatment, while PDGF had no effect. Therefore, while PDGF-Rα-dependent OPC proliferation and survival most probably does not initiate at the PC, still the integrity of this organelle and cilium-centered pathway is necessary for OPC survival and differentiation.

Targeting of vasoactive intestinal peptide receptor 2, VPAC2, a secretin family G-protein coupled receptor, to primary cilia

Primary cilia protrude from the cell surface of many cell types in the human body and function as cellular antennae via ciliary membrane localized receptors. Neurons and glial cells in the brain possess primary cilia, and the malfunction of primary cilia may contribute to neurological deficits present in many cilia-associated disorders. Several rhodopsin family G-protein coupled receptors (GPCRs) are specifically localized to a subset of neuronal primary cilia. However, whether other family GPCRs target to neuronal cilia and whether glial primary cilia harbor any GPCRs are not known. We conducted a screening of GPCRs to determine their ability to target to primary cilia, and identified a secretin family member, Vasoactive Intestinal Receptor 2 (VPAC2), as a novel ciliary GPCR. Here, we show that endogenous VPAC2 targets to primary cilia in various brain regions, including the suprachiasmatic nuclei and the thalamus. Surprisingly, VPAC2 not only localizes to neuronal cilia but also to glial cilia. In addition, we show that VPAC2's C-terminus is both necessary and sufficient for its ciliary targeting and we define a novel ciliary targeting signal: the tetrapeptide RDYR motif in the C-terminus of VPAC2. Furthermore, we demonstrate that VPAC2 ciliary targeting is dependent on Tubby, the BBSome (a complex of Bardet-Biedl syndrome proteins) and the BBSome targeting factor, Arl6.

Clear cell tumors of the central nervous system: a case-based review

Clear cell tumors of the central nervous system (CNS) encompass a variety of tumor subtypes that are challenging to diagnose given their similar morphologic features. Here, I use a case-based approach to review the clinicopathologic and radiologic features to help guide the general pathologist in the diagnosis of clear cell tumors of the CNS. First, the reader is invited to study 6 images of different CNS tumors with clear cell morphology. Then, each case is expanded in light of clinical and radiologic data and includes a histopathologic description of the tumor. A brief discussion follows with up-to-date diagnostic tools. Finally, I propose an immunohistochemical algorithm to navigate through the complex features that characterize clear cell tumors of the CNS. This review aims to provide a comprehensive approach to diagnosing clear cell neoplasms of the CNS based on improved assessment of the clinicopathologic and radiologic features of each entity.

Cerebellar gliomatosis in a toddler: case report of a challenging condition and review of the literature

Gliomatosis confined to the cerebellum is most unusual. We report such a case in a 20-month-old male who presented with unsteadiness. Magnetic resonance imaging revealed a diffuse area of abnormal signal intensity within both cerebellar hemispheres, which did not enhance after contrast administration. The patient underwent a biopsy, which revealed a diffuse glioma infiltrating the cerebellum. Overall, the tumor cells had oligodendroglioma-like features and exhibited only focal vimentin immunoreactivity. They were negative for glial fibrillary acidic protein, synaptophysin, βIII-tubulin, and neurofilament protein. Immunofluorescence, performed on primary biopsy explants maintained in cell culture without exposure to growth factors or differentiation-promoting agents, revealed widespread nestin immunoreactivity and immunolabeling of occasional cells with antibodies to platelet-derived growth factor-α and O1/O4, markers of oligodendrocyte precursor-cells and immature oligodendrocytes, respectively. Fluorescent in situ hybridization performed on explants, touch preparations, and paraffin sections failed to reveal loss of heterozygosity for either 1p36 or 19q13. The patient was treated with temozolomide and remains stable, albeit with residual quiescent tumor, more than 3 years after surgery. This report calls attention to an unusual presentation of gliomatosis confined to the cerebellum of a toddler and addresses salient aspects of clinical and radiological differential diagnosis, as well as therapeutic challenges encountered.

Cilia in the CNS: the quiet organelle claims center stage

The primary cilium is a cellular organelle that is almost ubiquitous in eukaryotes, yet its functions in vertebrates have been slow to emerge. The last fifteen years have been marked by accelerating insight into the biology of primary cilia, arising from the synergy of three major lines of research. These research programs describe a specialized mode of protein trafficking in cilia, reveal that genetic disruptions of primary cilia cause complex human disease syndromes, and establish that Sonic hedgehog (Shh) signal transduction requires the primary cilium. New lines of research have branched off to investigate the role of primary cilia in neuronal signaling, adult neurogenesis, and brain tumor formation. We review a fast expanding literature to determine what we now know about the primary cilium in the developing and adult CNS and what new directions should lead to further clarity.

Hydroxysteroid sulfotransferase 2B1b expression and localization in normal human brain

Steroid sulfonation in the human brain has not been well characterized. The major sulfotransferase (SULT) isoforms that conjugate steroids in humans are SULT1E1, SULT2A1, and SULT2B1b. SULT2B1b catalyzes the sulfonation of 3β-hydroxysteroids, including neurosteroids dehydroepiandrosterone and pregnenolone, as well as cholesterol and several hydroxycholesterols. SULT2B1b mRNA and protein expression were detected in adult and fetal human brain sections, whereas neither mRNA, nor protein expression were identified for SULT1E1 or SULT2A1. Using immunohistochemical analysis, SULT2B1b expression was detected in neurons and oligodendrocytes in adult brain and in epithelial tissues in 28-week-old fetal brain. Sulfonation of cholesterol, oxysterols, and neurosteroids in the brain is apparently catalyzed by SULT2B1b since expression of neither SULT2A1 nor SULT1E1 was detected in human brain sections. SULT2B1b mRNA and protein were also detected in human U373-MG glioblastoma cells. Both mRNA and protein expression of liver X receptor (LXR)-β, but not LXR-α, were detected in U373-MG cells, and LXR-β activation resulted in a decrease in SULT2B1b protein expression. Since hydroxycholesterols are important physiological LXR activators, this suggests a role for regulation of sterol metabolism by LXR and SULT2B1b. Therefore, elucidating key enzymes in the metabolism of cholesterol and neurosteroids could help define the properties of steroid conjugation in the human brain.

Differentiation of clear cell ependymoma of the cerebellum from hemangioblastoma by thallium-201 single photon emission computed tomography-case report-

A 57-year-old man suffered from dizziness for about one year and truncal ataxia for about one month. Magnetic resonance imaging demonstrated a cystic tumor with a homogeneously enhanced mural nodule located in the cerebellar vermis. Computed tomography angiography revealed a hypervascular nodule. These findings were compatible with hemangioblastoma. Thallium-201 single photon emission computed tomography ((201)Tl-SPECT) showed moderately high uptake in the early phase and moderately high retention in the delayed phase, whereas hemangioblastoma shows almost no retention in the delayed phase. The patient underwent total removal of the tumor. The histological diagnosis was clear cell ependymoma (CCE). CCE is a rare subtype of ependymoma, which resembles hemangioblastoma in histological and neuroimaging findings, but is considerably more aggressive. (201)Tl-SPECT can provide useful information for the preoperative differential diagnosis of infratentorial CCE and hemangioblastoma.

Clear-cell Ependymoma of the Cerebellum: A Case Report

A case of clear-cell ependymoma occurring in the cerebellum of a 3-year-old girl is reported. Light-microscopically, the tumor consisted mainly of clear cells with a perinuclear halo and showed some vague perivascular pseudorosettes, not true rosettes. In addition, the histological features of anaplasia, characterized by increased mitosis and focal pseudopalisading necrosis, were also observed. Immunohistochemically, the tumor cells were focally positive for glial fibrillary acidic protein and weakly positive for epithelial membrane antigen. Ultrastructurally, the intermediate junctions and rudimentary cilia confirmed the ependymal differentiation. Fifteen cases of infratentorial clear-cell ependymoma have been reported to date, and this case is the second childhood tumor among them, to the best of the authors' knowledge.

Clear cell ependymoma of the temporal lobe in a child: a case report

A 12-year-old boy with a left temporal tumor diagnosed as clear cell ependymoma (CCE) was reported. CCE is an uncommon central variant of ependymomas with a predilection for the supratentorial region in children. Brain tumors with a honeycomb pattern with clear cells having round nuclei and perinuclear halos could pose a problem in the differential diagnosis with the other tumors with clear cells. There were 41 reported cases of CCE in the literature. In 61% of these cases, tumors were located in the supratentorial region, and in the others in the posterior fossa and spinal cord. However, there was none located in the temporal lobe except in the case presented here.

Neuronal features of oligodendrogliomas--an ultrastructural and immunohistochemical study

AIMS

To assess neuronal differentiation in oligodendrogliomas (ODGs).

METHODS AND RESULTS

An electron microscopic and immunohistochemical study of 41 consecutive cases was performed. In all cases, tumour cells with neuritic structures were identified ultrastructurally, including synapses and neurosecretory granules. For the immunohistochemical identification of synaptophysin, monoclonal antibody clones 27G12, Snp88 and SY38 and a polyclonal antibody were compared in optimized protocols on slides from a spectrum of tissues and 16 ODGs. 27G12 gave the best signal-to-noise ratio, while SY38 gave the poorest. When 27G12 was applied on all 41 ODGs, widespread immunoreactivity was obtained in 100%. Among three antibodies to chromogranin compared similarly, clone LK2H10 and a polyclonal antibody gave identical patterns of immunoreactivity, whereas clone DAK-A3 gave weaker reactions. When LK2H10 was applied on all tumours, staining was found in 12 (29%). All tumours but one stained strongly for glial fibrillary acidic protein and all for synapsin I. Fluorescence in situ hybridization analysis showed a concomitant 1p/19q deletion in 12/16 ODGs.

CONCLUSIONS

Our study provides evidence for widespread neuronal differentiation in ODGs, suggesting that these tumours may be derived from progenitor cells with limited commitment. Antibody selection and protocol optimization are mandatory for reliable immunohistochemistry results.

Oligodendroglioma with neurocytic differentiation versus atypical extraventricular neurocytoma: a case report of unusual pathologic findings of a spinal cord tumor

Differentiating oligodendroglioma from extraventricular neurocytoma by conventional light microscopy alone can present a diagnostic challenge. We report pathologic findings of an unusual spinal cord tumor from a 33-year-old male patient which showed hybrid features of oligodendroglioma and extraventricular neurocytoma. Magnetic resonance imaging (MRI) showed an enhancing intramedullary mass in the cervicothoracic region (C7 through T6). Histologic examination revealed a clear cell neoplasm containing ganglion-like cells and calcifications, prompting the differential diagnosis of oligodendroglioma and extraventricular neurocytoma. The immunohistochemical analysis disclosed neural differentiation of the neoplastic cells with strong synaptophysin and neurofilament staining consistent with extraventricular neurocytoma, as well as strong S-100 and glial fibrillary acidic protein (GFAP) expression. Molecular studies with fluorescent in situ hybridization (FISH) revealed chromosome 1p/(partial) 19q deletions, a finding commonly observed in oligodendroglioma. The proliferation index (using antibody MIB1) of the tumor was approximately 30%. The morphologic findings and these results strengthen the hypothesis that these tumors may share a common progenitor cell, which has also been observed by others. Because there are differences in patient management and long-term prognosis, it is important to attempt to distinguish between oligodendroglioma and neurocytoma. This unusual case and similar rare reported cases support the need to reclassify tumors showing pathologic features common to both neurocytoma and oligodendroglioma as a unique entity, while the effort continues to identify the cell of origin.

Proteomics analysis of human astrocytes expressing the HIV protein Tat

Astrocyte infection in HIV has been associated with rapid progression of dementia in a subset of HIV/AIDS patients. Astrogliosis and microglial activation are observed in areas of axonal and dendritic damage in HIVD. In HIV-infected astrocytes, the regulatory gene tat is over expressed and mRNA levels for Tat are elevated in brain extracts from individuals with HIV-1 dementia. Tat can be detected in HIV-infected astrocytes in vivo. The HIV-1 protein Tat transactivates viral and cellular gene expression, is actively secreted mainly from astrocytes, microglia and macrophages, into the extracellular environment, and is taken up by neighboring uninfected cells such as neurons. The HIV-1 protein Tat released from astrocytes reportedly produces trimming of neurites, mitochondrial dysfunction and cell death in neurons, while protecting its host, the astrocyte. We utilized proteomics to investigate protein expression changes in human astrocytes intracellularly expressing Tat (SVGA-Tat). By coupling 2D fingerprinting and identification of proteins by mass spectrometry, we identified phosphatase 2A, isocitrate dehydrogenase, nuclear ribonucleoprotein A1, Rho GDP dissociation inhibitor alpha, beta-tubulin, crocalbin like protein/calumenin, and vimentin/alpha-tubulin to have decreased protein expression levels in SVGA-Tat cells compared to the SVGA-pcDNA cells. Heat shock protein 70, heme oxygenase-1, and inducible nitric oxide synthase were found to have increased protein expression in SVGA-Tat cells compared to controls by slotblot technique. These findings are discussed with reference to astrocytes serving as a reservoir for the HIV virus and how Tat promotes survival of the astrocytic host.

Clear cell ependymoma of the fourth ventricle

Two cases of clear cell ependymoma (CCE) of the fourth ventricle are reported in a 49-year-old woman with dysphagia and a 59-year-old woman with dizziness and gait disturbance. CCE is a relatively new variant of ependymoma added to the WHO classification of tumors in 1993. Tumor cells display an oligodendroglioma-like appearance with a clear perinuclear halo. Most infratentorial CCE tumors are located in the cerebellum. There are only three cases, including the present two cases, that have been reported to affect the fourth ventricle.

Atypical extraventricular neurocytoma with oligodendroglioma-like spread and an unusual pattern of chromosome 1p and 19q loss

An insular cortex tumor in a 54-year-old woman showed unequivocal neurocytic features, including open nuclei, distinct nucleoli, and strong synaptophysin immunoreactivity. Ultrastructurally, there were neuritic-type processes with microtubules and hillock-like attachments, and there were dense-core granules. Atypical features were mitotic activity, prominent vasculature, and small foci of necrosis. Peripherally, there was oligodendroglia-like histology with single-cell infiltration of white matter and perineuronal spread in cortex. Fluorescence in situ hybridization analysis with chromosome 1 and 19 probes showed 3 copies of 1q and 2 copies of 1p and showed 2 copies of 19q and 4 copies of 19p. This yielded a 1p-19q loss of heterozygosity pattern similar to that seen in oligodendrogliomas, although the actual chromosomal abnormality is distinct. This tumor, best classified as an atypical neurocytoma with oligodendroglia-like spread, supports suggestions of a close histogenic relationship between oligodendroglial and neurocytic tumors. This case also illustrates the limitations of relying exclusively on loss of heterozygosity analysis for tumor classification.

Clear cell ependymoma with a lipidized component that developed in the thoracic spinal cord

The authors report a case of clear cell ependymoma with a lipidized component that developed in the thoracic spinal cord. A 59-year-old man was admitted to the hospital with an itchy pain in the left forearm to the left anterior and lateral chest for the past three years. Neurological findings on admission included dissociated sensory disturbance below the C8 level and increased deep tendon reflex in both lower extremities. An MRI scan of the spinal cord revealed an intramedullary tumor with a longer diameter of 3.5 cm at the T3-T4 level and a distended syrinx at the T2-T3 level. Surgery was performed after T1-T5 laminectomy. The gray, soft and well demarcated tumor was removed subtotally. Light microscopy revealed a portion where clear cells proliferated and a portion where foamy cells proliferated. In some tissue, there were a very few nuclear areas suggestive of a perivascular pseudorosette. Neither nuclear division nor necrosis was observed. Immunohistochemically, the tumor cells were positive for glial fibrillary acidic protein (GFAP), epithelial membrane antigen (EMA), vimentin, and negative for cytokeratin, synaptophysin. The MIB-1 staining index was 0.25%. Based on these findings, diagnosis of clear cell ependymoma with a lipidized component was made.

Extraventricular neurocytoma: morphological and immunohistochemical considerations on differential diagnosis

Neurocytoma is an unusual neuronal tumor especially affecting young people. It commonly arises in the ventricles and has a benign outcome. Herein, we report on a rare case of extraventricular neurocytomas (right parietal lobe) in a young girl admitted to hospital for a cranial trauma subsequent to a seizure. The tumor, radiologically well-circumscribed, cystic and enhancing, was surgically excised. The patient, who received no post surgical treatment, is alive and well after 18 months of follow-up. Pathological examination showed a well-differentiated lesion composed of uniform, round cells with perinuclear halos in a neuropil background and immunohistochemically positive for neuronal markers (synaptophysin, neuron-specific enolase, neurofilaments). The authors emphasize the role of the morphological and immunohistochemical evaluations to recognize this rare tumor.

The Big Eye in the 21st century: the role of electron microscopy in modern diagnostic neuropathology

Electron microscopy (EM) remains a powerful and even essential tool in modern diagnostic neuropathology. tumors are still encountered that defy histological or immunohistochemical classification, and EM can often provide answers in these cases. Tumors of the CNS for which EM is useful include unusual or atypical variants of meningioma, ependymoma, and schwannoma; oligodendroglioma-like tumors composed of small "clear" cells; and small "blue cell" tumors of childhood. EM is of great value in identifying site of origin for metastatic adenocarcinomas of unknown origin-an under-recognized and under-utilized potential for this technique. EM is useful in the diagnosis of peripheral nerve sheath tumors and gastrointestinal autonomic nerve tumors. EM is also important in the evaluation of certain congenital, inherited and metabolic diseases-including ceroid lipofuscinoses, CADASIL syndrome, certain myopathies, and mitochondrial encephalomyopathies--and of certain toxic and drug-induced peripheral neuropathies. An important application of EM is its utility in initiating a workup of an atypical tumor or metabolic condition, for which clinical and histological clues point in no obvious direction. In these situations, EM may provide either an answer outright (including answers to questions not asked) or important clues that guide further workup and narrow the range of diagnostic possibilities.

Oligodendroglioma: pathology and molecular biology

BACKGROUND

Recently, important new information has become available concerning the histologic recognition and molecular biology of oligodendrogliomas. This information, in turn, impacts the way neurosurgeons diagnose and treat patients with these tumors. The purpose of this paper is to review the pathology and basic science of oligodendroglioma, highlighting these developments.

METHODS

Information for this review was obtained by a Medline search using the term "oligodendroglioma," and limiting the results to articles dealing with pathology. Chapters from standard textbooks were also used, and bibliographies were checked for additional key articles contributing to the understanding of the pathobiology of this disease.

RESULTS

On histologic examination, oligodendrogliomas must be differentiated from tumors including the fibrillary astrocytoma, clear cell ependymoma, central neurocytoma, and dysembryoplastic neuroepithelial tumor (DNT). There is no specific immunocytochemical marker allowing for the recognition of human oligodendroglial tumor cells. A current simplified grading scheme separates these tumors into low grade (WHO grade II) and anaplastic (WHO grade III) oligodendrogliomas. New molecular and genetic markers may aid in grading oligodendrogliomas and identifying patients with a better prognosis or response to chemotherapy. Markers studied include Ki-67, PCNA, EGFr, VEGF, platelet-derived growth factor, p16, p18, p53, bcl-2, COX-1, and chromosomal deletions. The combination of allelic losses on chromosomes 1p and 19q has been statistically associated with a longer recurrence-free survival after chemotherapy.

CONCLUSIONS

A patient with an oligodendroglioma may at times still present a diagnostic challenge for the neuropathologist. Yet making an accurate diagnosis is essential, since the clinical course and optimal therapeutic approach differs from that of other gliomas. In the near future, molecular characterization of oligodendrogliomas is expected to play an even greater clinical role.

Current diagnosis and treatment of oligodendroglioma

Object

The strategies used to diagnose and treat oligodendroglial tumors have changed significantly over the past decade. The purpose of this paper is to review the topic of oligodendroglioma, emphasizing the new developments.

Methods

Information was obtained by conducting a Medline search in which the term oligodendroglioma was used. Recent editions of standard textbooks were also studied.

Because of tools such as magnetic resonance imaging, oligodendrogliomas are being diagnosed earlier, and they are being recognized more frequently histologically than in the past. Seizures are common in these patients. Functional mapping and image-guided surgery may now allow for a safer and more complete resection, especially when tumors are located in difficult areas. Genetic analysis and positron emission tomography may provide data that supplement the standard diagnostic tools. Unlike other low-grade gliomas, patients in whom residual or recurrent oligodendroglioma (World Health Organization Grade II) is present may respond to chemotherapy. Although postoperative radiotherapy prolongs survival of the patient, increasingly this therapeutic modality is being delayed until tumor recurrence, especially if a gross-total tumor resection has been achieved. Oligodendrogliomas are the first type of brain tumor for which “molecular” characterization gives important information. The most significant finding is that allelic losses on chromosomes 1p and 19q indicate a favorable response to chemotherapy.

Conclusions

Whereas surgery continues to be the primary treatment for oligodendroglioma, the scheme for postoperative therapy has shifted, primarily because of the lesion's relative chemosensitivity. Molecular characterization of oligodendrogliomas may become a standard practice in the near future.

Intramedullary Clear Cell Ependymoma in the Cervical Spinal Cord: Case Report

OBJECTIVE AND IMPORTANCE

Clear cell ependymoma of the spinal cord has not been reported in the literature, although ependymoma in the cerebral and cerebellar hemispheres has been described. We present the first case report of this rare histological type of ependymoma arising in the cervical spinal cord and emphasize the importance of recognizing this histological entity.

CLINICAL PRESENTATION

A 42-year-old woman presented with numbness in both upper limbs and spastic gait. Magnetic resonance imaging revealed an intramedullary tumor at the C6–T1 level with syringomyelia.

INTERVENTION

The tumor was totally removed. Histological analysis revealed that the tumor was composed of round cells with perinuclear halos similar to those observed in oligodendroglioma. However, we diagnosed clear cell ependymoma because these tumor cells exhibited epithelial features and ependymal rosettes under light microscopic examination.

CONCLUSION

Histological diagnosis was crucial to our determining whether to perform postoperative adjuvant therapy in this patient. Neurosurgeons should be aware of the possibility of this histological entity among intramedullary spinal cord tumors.

Central neurocytomas are genetically distinct from oligodendrogliomas and neuroblastomas

AIMS

Central neurocytoma is a rare central nervous system tumour typically found in the lateral ventricles and at the septum pellucidum. Histologically, it resembles oligodendrogliomas and yet ultrastructurally, it shows neuronal differentiation. Its molecular oncogenesis is not known. The aim of this study was to examine whether major genetic events found in oligodendrogliomas and neuronal tumours, namely allelic deletions of chromosomes 1p and 19q and N-myc amplification, can be found in central neurocytomas. As there was one report describing gain of chromosome 7 in central neurocytomas, we also examined epidermal growth factor receptor (EGFR) amplification, as the EGFR gene is located at chromosome 7p.

METHODS AND RESULTS

Nine central neurocytomas and matched blood samples were examined for loss of heterozygosity (LOH) of 1p and 19q13.2-13.4 with 23 finely mapped microsatellite markers. N-myc amplification was studied by fluorescence in-situ hybridization using paraffin-embedded sections. EGFR amplification was tested for by differential PCR. Six of nine (67%) tumours showed LOH at one or more loci at 1p and 5/9 (56%) of cases showed LOH at 19q. However, common regions of deletion cannot be identified. The majority of informative markers are retained at 1p (84%) and 19q (86%). Only one tumour showed amplification of N-myc and none of the cases showed amplification of EGFR.

CONCLUSION

Central neurocytomas are genetically distinct from oligodendrogliomas, and chromosomes 1p and 19q probably do not play an important role in their pathogenesis. N-myc and EGFR amplification are rare.

Pigmented central neurocytoma: case report and literature review

A case of pigmented central neurocytoma is reported. The tumor showed histologic, immunophenotypic, and ultrastructural features of central neurocytoma. The pigment consisted of an intimate association of lipofuscin and neuromelanin. Pigmented neuroepithelial tumors are rare, and the pigments may be neuromelanin or melanin. Pigmented central neurocytoma has not been described to date. The low proliferation rate of the tumor suggests a delayed turnover of tumor cells as a possible cause of lipofuscin accumulation. Autocatalytic peroxidation of lipofuscin is a possible mechanism of neuromelanin formation.

Mucin-secreting cellular ependymoma: a light and electron microscopy study

Mucin accumulation in ependymomas is thought to be limited to the myxopapillary variant and represents an important diagnostic feature. Similarly, signet-ring cells in ependymomas have been shown by electron microscopy to represent microrosette instead of mucin secretion. This study describes an infratentorial ependymoma largely composed of mucinous areas and signet-ring cells. The ependymal nature of mucin-secreting cells was confirmed by ultrastructural analysis. This case widens the variable spectrum of ependymal morphology. The value of electron microscopy in differentiating central nervous system neoplasms showing mucous secretion is stressed.